The fate and erosion history of abandoned artificial islands in the Beaufort Sea
Canadian Seabed Research Ltd.
Canadian Coast Guard
Atlantic Geoscience Centre
Halifax, N.S. : Canadian Seabed Research Ltd., 1990.
xi, 65 leaves : ill. (some col.), maps ; 30 cm.
Bound in loose-leaf binder.
Thirteen folded maps in pockets.
ASTIS record 46233.
Over 30 artificial islands have been constructed in the shallow water region of the Canadian Beaufort Sea since the early 1970s. These structures were used as stable drilling platforms, but then abandoned and left to the natural elements of wind, waves and ice to erode. This study was initiated to help assess the degree of hazard these sites may pose to navigable waters in the Beaufort Sea region. The fate and erosion history of four abandoned artificial islands; Arnak L-30, Issungnak O-61, Itiyok I-27 and Kaubvik I-43 are examined in this report. The erosional morphology of these submerged features can be generalized as having roughly concentric to oblong dimensions with the steepest slopes occurring on the landward side. This southeast section of the islands is also where the shoalest water depths occurred for all four sites which ranged from 3.0 m for Arnak to 3.7 m for Itoyok. This morphology results from erosion of the (higher
energy) seaward slopes with the entrained sediment deposited on the (lower energy) lee slope. The seabed foundation that the islands are all built on ... [consists of] Unit A clays and silt. By contrast, the islands themselves are constructed of fine to coarse sand and gravel. The presence of sand on the island crest was confirmed by side scan sonar data, however, the interpretation of gravel was constrained by the possibility of construction debris in the area. Sediment transport bedforms were found at all four sites which indicate that entrainment and transport of the island sediments is occurring, at least during major storms. ... An important aspect of this study was the identification of possible debris features left on the island's surface after abandonment. Such materials might include; dredge pipes, drill pipe, drilling mud barrels, sand bags, filter cloth, chain link fence, cable netting and soil anchors. Although the operators were
required to clean the island's surface upon abandonment, there is some evidence to suggest that these operations were inadequate. The exact identity of each target type is difficult to confirm based on the acoustic, side scan sonar data alone. ... Analysis of the 1989 survey data and review of the historic literature allow us to summarize our interpretation regarding erosion rates of artificial islands in the Beaufort Sea as follows; 1) The rate and depth to which islands will ultimately erode is controlled by water depth and the frequency of extreme storm wave conditions. 2) Those islands in deeper water become submerged within 2 or 3 years, whereas those in very shallow water (2 m or less) do not erode as rapidly to the water line. 3) The vertical erosion rate, following submergence is initially high, but decreases with time. The islands appear to approach an equilibrium elevation between -3 and -5 m, within 5 to 15 years of abandonment. This
elevation depends on ambient water depth, with islands in depths greater than 20 m, decreasing to an elevation of -5 m. 4) The islands all show an increase in diameter with time in at least one dimension, that usually indicates sediment transport towards the southeast. The islands therefore appear to migrate landward at rates of up to 10-20 m/year. There is no evidence in the present data for a stabilization of this lateral motion, although a slow down might be expected as the island elevation becomes stabilized. 5) Once the equilibrium elevation has been attained, the islands will probably not be significantly lowered by natural processes over the next 100 years, except by the occurrence of extreme storms. Such events have return periods greater than 10 years. It is unlikely that any island would be eroded to much below -5 m within a time period of several decades. [The following information is provided for each artificial island on the folded
map sheets: Oil Company Operator, construction start date, construction end date, spud date, rig release date, date abandoned, water depth (m), type of island structure, construc tion method, aggregate source site, volume of aggregate (m³), island dimensions (surface), surface height MSL (m), slope below MSL and beach/berm protection.]
Granular borrow and fill quality at selected locations in the Canadian Beaufort Sea
Klohn-Crippen Consultants Ltd.
Canada. Indian and Northern Affairs Canada
Calgary, Alta. : Klohn-Crippen Consultants Ltd., 1997.
ii, iv, 35,  leaves : ill. (some folded), maps (some folded) ; 30 cm.
ASTIS record 46309.
Since the early 1970's, approximately 40 million cubic metres of granular material have been dredged within the Canadian Beaufort continental shelf to create artificial islands or subsea berms for caisson retained islands and drilling barges. These islands were constructed to provide temporary drilling structures for hydrocarbon exploration. After completing drilling and removing the equipment and consumables, these islands were abandoned to natural erosion, or partially scalped and reused at other exploration sites. The purpose of this report is to document the available sources of good quality granular material in the abandoned islands located in the Canadian Beaufort Sea. The report documents the seabed borrow locations which were the original source of the coarser fill material and presents more detailed information on the islands in which the coarser fill material was placed. The gradation of the material in the islands is detailed
when quality assurance test data is available. The data suggests that there is a gradual loss of the fines compared to the original borrow source when the material is reused. This can be expected due to the dredging and submarine deposition process. This database was prepared ... on behalf of the Department of Indian and Northern Affairs, Canada, as part of the Northern Granular Resources Program. Mr. Bob Gowan was the scientific officer for the project. The Klohn-Crippen report titled "Granular Resource Potential of Beaufort Artificial Islands" dated March 1995 was reviewed to assess which of the abandoned islands were most suitable for a more detailed review of the granular materials used in construction, in terms of information collected at the borrow source(s), during construction, and during post construction investigations. The 1995 report documented 37 islands in the Canadian Beaufort Shelf which were believed to represent the total
number of offshore islands constructed in the area. A tabular listing of the as-built quantities required for each island, the borrow source and a description of the fill material is included in Table 1.1.
CPT data, artificial islands, Canadian Beaufort Sea : final report
Klohn-Crippen Consultants Ltd.
Canada. Indian and Northern Affairs Canada
Calgary, Alta. : Klohn-Crippen Consultants Ltd., 1999.
i, iv, 44,  leaves : ill. (some folded), maps (some folded) ; 30 cm.
ASTIS record 46311.
Approximately 40 million cubic metres of granular material have been dredged within the Canadian Beaufort continental shelf to create artificial islands or subsea berms for caisson retained islands and drilling barges. These islands were constructed to provide temporary drilling structures for hydrocarbon exploration. After completing drilling and removing the equipment and consumables, these islands were abandoned to natural erosion, or partially scalped and reused at other exploration sites. A series of reports by Klohn-Crippen Consultants Ltd. for the Department of Indian and Northern Affairs, Canada, have documented the available sources of good quality granular material located in the Candian Beaufort Sea that could potentially be used in future developments. Documentation covers the seabed borrow locations which were the original source of the coarser fill material, summarizes the construction history of all the old islands, and
documents further fill quality information on eleven of the abandoned islands in which the coarser fill material was placed. Information on insitu density was monitored by deploying the cone penetration test (CPT). This report provides a summary of the available CPT data for the key abandoned islands that provide the delineated sand and gravel borrow source, and also documents CPT data from some additional sites in the Canadian Beaufort Sea, namely the Nerlerk B-67 berm, the Isserk I-15 Molikpaq deployment site, and at trial berm sites that used Isserk and Ukalerk borrow material. In total the report documents 422 cone penetration tests completed at nine island sites and three trial berm sites. ... [It is recommended that this report be read in conjunction with the June 1997 report on Granular Borrow and Fill Quality which documents the material used in the construction of selected artificial islands.]